Detection of adulteration of kudzu powder by terahertz time-domain spectroscopy

Abstract

In this paper, the terahertz time-domain spectroscopy (THz-TDS) combined with chemometric methods, is used to explore the rapid and undamaged detection of kudzu powder’s adulteration. The spectral data in the range of 0.1–7 THz is collected. The absorption coefficient of the 0.5–3.0 THz band is selected for analysis. The chemometric methods are adopted to build the analytical model of the spectrum’s absorption coefficient. In qualitative modelling, the partial least squares decision analysis (PLS-DA) analyses the absorption coefficient data. The result shows that the misjudgment rate is 57.6%. The least squares support vector machines decision analysis (LS-SVM-DA) basing on Linear (LIN), and radial basis function (RBF) as the kernel function is used to analyze the data, the results show that the misjudgment rate is all 13.3%. Finally, the successive projections algorithm (SPA) and the elimination of uninformative variables (UVE) are used to select the spectrum's absorption coefficient to optimize the model, the misjudgment rates of PLS-DA model basing on SPA and UVE are 33.3% and 23.3%, respectively. The LIN of LS-SVM-DA and the RBF of LS-SVM-DA basing on SPA are all 43.3%, the misjudgment rates of the LIN of LS-SVM-DA and the RBF of LS-SVM-DA basing on UVE are13.3% and 6.7%, respectively. The comparison found that the RBF of LS-SVM-DA basing on the UVE prediction model for the adulteration of kudzu powder is more accurate than the others. It can come true the judgment of adulteration of kudzu powder well. Studies have shown that THz-TDS combined with chemometric methods can provide a fast and accurate analytical way for qualitative analysis of kudzu powder's adulteration.